Temperature controlled cargo containers, such as refrigerated trailers, are commonly used to transport food products and other temperature sensitive products. A refrigerated trailer typically includes a refrigeration unit generally mounted on the front wall of the trailer with a portion protruding into the interior of the trailer. In some known trailers, a fuel-burning engine may be used to drive a compressor of the refrigeration system.
Fuel usage and fuel efficiency is critical in the evaluation of transportation refrigeration systems. To reduce the fuel usage or improve fuel efficiency, particularly at part load conditions, some transportations refrigeration systems have moved from single speed technology to Variable Frequency Drive (VFD) or Multi-Speed Drive (MSD) technologies. Proper control of the VFD's and MSD's is required in order to achieve measurable improvement.